Fresh from helping to choose the next CEO to run the company he co-founded nearly four decades ago, Gates descended from the mountaintop to mix it up with the new media masses with his second Reddit appearance in the last year.

Even before the festivities officially got underway, Gates posted a video where he answered a question ahead of time by someone left on the Reddit board asking where he would pick up a $100 bill if he saw the money lying on the ground.

"Well, all my thoughts about money were formed at a time when $100 really was a substantial amount of money...if it's lying there and maybe it belongs to somebody and you ought to find it for them and return it to them," he said. "It'd be nice. They'd probably be fairly distraught about having dropped it. But i would pick it up and give it to the foundation because there, $100 actually buys quite a bit."

Then the conversation took a more serious turn.

Asked about his new role -- Microsoft last week announced that he was stepping down as company chairman but would increase his participation as a technology advisor to newly-appointed CEO Satya Nadella , Gates avoided directly answering the question.

Gates said he's excited to take a more active role at Microsoft under new CEO Satya Nadella.

(Credit: Microsoft)

"I am excited about how the cloud and new devices can help us communicate and collaborate in new ways. The OS won't just be on one device and the information won't just be files - it will be your history including being able to review memories of things like kids growing up. I was thrilled Satya asked me to pitch in to make sure Microsoft is ambitious with its innovation. Even in Office there is a lot more than can be done."

Asked to weigh in on the growing debate around the NSA's surveillance practices , Gates avoided any potential shoals by hitching himself to a safe position somewhere in the middle.

"This is a complex issue," Gates wrote. "Privacy will be increasingly important as cameras and GPS sensors are gathering information to try and be helpful. We need to have trust in the way information is protected and gathered. There is a role for the government to try and stop crime and terrorism but it will have to be more open. I do think terrorism with biological or nuclear weapons is something we want to minimize the chance of."

One wiseheimer on the thread said his money was on "not getting an answer to this." Gates, showing more flashes of public humor than he did back when the Justice Department and Janet Reno were on his case, supplied a quick riposte.

"I did answer unless the NSA deletes my answer."

He also offered advice to current computer science students about where they might devote special attention.

"The ultimate is computers that learn. So called deep learning which started at Microsoft and is now being used by many researchers looks like a real advance that may finally learn. It has already made a big difference in video and audio recognition - more progress in the last 3 years than ever before." He subsequently elaborated, while noting that terms can be confusing. "Learning can mean a low level thing which all machine learning algorithms do or the high level idea of reading a book and understanding what it means."

Offering an aside that computer historians will want to squirrel away, Gates revealed his favorite project while working at Microsoft.

"The Windows project which required a lot of patience was great. Office was also great. Together they defined the big success of the 1990s for Microsoft. Office connected to the cloud has a LOT of potential and we are off to a good start.Cloud Storage needs to be a lot richer though."

Later on during the thread, Gates also received the inevitable "where the future of computing heading" question.

"The boundaries between form factors is blurring but the range of screen sizes and different input techniques will still mean there are desktop devices and wall devices. However applications will be able to run across multiple devices including the whiteboard."

Gates, who knows how to navigate the role of elder statesman in the tech industry, also declined to get drawn into offering advice to younger entrepreneurs about how they ought go about balancing business and philanthropy. Instead, he wrote that "just creating an innovative company is a huge contribution to the world" would suffice. "During my 20's and 30's that was all I focused on. Ideally people can start to mix in some philanthropy like Mark Zuckerberg has early in his career. I have enjoyed talking to some of the Valley entrepreneurs about this and I am impressed and how early they are thinking about giving back - much earlier than I did."

This being Reddit, and thus a free-for-all, the questions came from all corners.So it was that someone asked about the Gates Foundation's sponsorship of a competition to design a more comfortable and functional condom.

"This is a sensitive topic. The idea was that men don't like the current design so perhaps something they would be more open to would allow for less HIV transmission. We still haven't gotten the results. One grantee is using carbon nanotubes to reduce the thickness."

He also fessed up to a question about his "most expensive guilty pleasure purchase?"

"Owning a plane is a guilty pleasure. Warren Buffett called his the Indefensible. I do get to a lot of places for Foundation work I wouldn't be able to go to without it."

Gates also seemed unenthusiastic about Bitcoin's potential as a digital currency.He drew a comparison with a digital money initiative sponsored by the Gates Foundation, noting that "unlike Bitcoin it would not be anonymous digital money. In Kenya M-pesa is being used for almost half of all transactions. Digital money has low transaction costs which is great for the poor because they need to do financial transactions with small amounts of money. Over the next 5 years I think digital money will catch on in India and parts of Africa and help the poorest a lot."

Over the decades, Gates has remarkably avoided getting caught up with Washington politics. That wasn't going to change Monday when he was asked what big domestic issue the government needed to address.

"Education would be the top issue since it is key to individual opportunity and to the country as a whole and we are not doing as well as other countries. After that I would say immigration since the injustice of the current system is incredible." He later added to that response, extending that beyond US borders."The greatest tragedy is kids who die or never get enough food to develop physically or mentally to achieve their potential. We need vaccines and nutrition to solve this. We are making progress but not fast enough. Cynicism is the biggest barrier."

And so what does the company co-founder use as his own personal tabletcomputer?